When you create an SMT part, all pads are set to top layer.  Similarly,
silkscreen goes on top overlay.

When placing these components, changing the component layer to bottom, moves
the pads to bottom layer, silkscreen to bottom overlay, and mirrors both.

The effect being that SMT components on the top layer have no interference
with SMT components on the bottom layer, even if an x-ray view shows them to
be on top of each other.

Any through-hole objects are added when laying out the board, and are not a
part of these SMT components.  See supplied libraries, or play with the
component wizard for examples.




-----Original Message-----
From: Robison Michael R CNIN [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, February 20, 2002 2:37 PM
To: 'Protel EDA Forum'
Subject: [PEDA] how does smt work ??


hello,

well, thats a pretty dumb question, isn't it?  hahaha.
but i'm serious.  i'm trying to reproduce a board which
has smt top and bottom, and it appears that some of the
smt pads overlap from top to bottom.  

so how do smt pads work?  on a thru-hole, they obviously
go thru the entire board.  how far does a pad go thru as
an smt?  obviously it has to at least burrow thru to any
layer it runs on, but do top and bottom overlapping smt 
pads necessarily net together?  i'm confused.

let me state that i realize many complex things are 
possible (blind and buried vias come to my mind), but
somehow i don't think this is the case with this board.
but i'm not sure.

thanks, miker

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